1. Field of the Invention
This invention relates to wiring units constituting wiring blocks, in which various circuit elements are connected.
2. Description of the Prior Art
Heretofore, printed circuits which are formed by printing a copper foil in a predetermined wiring pattern on an insulating substrate chiefly composed of resins, have been used as the wiring block. However, the substrate of the printed circuit is subject to warping or bowing with a change in ambient temperature, resulting in breakage of the copper foil and open-circuit conditions. Also, when the substrate is wetted with moisture, its insulating property is likely to deteriorate, so that such undesired results as discharge and burn-out are liable to occur. Further a number of chemical treatments are indispensable for etching the copper foil, and this is liable to lead to public environment pollution problems.